Cathode structure



Nov. 2, 1965 .1. MoNTGAlLLARD GATHODE STRUCTURE Filed Nov. 1, 1962 w?baDDDDDDDDD [lll INVEN-ron: J- Mo/vrGA/L ARD BY @mi W7.

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United States Patent O CA'EHGDE STRUCTURE .lean Montgaillard, Paris,France, assigner' to CSF-Compagnie Generale de Telegraplhie Sans Fil,Paris, France Filed Nov. ll, 1962, Ser. No. 234,699 Claims priority,application France, Nov. 9, 11961,

7 Claims. (Cl. 313-270) The cathode of certain electron tubes is oftenconstituted by an emissive cylinder or disk, supported in an over hungor suspended manner by a hollow cylinder normally referred to as ski1t;this skirt is secured to a solid or rigid piece, frequently taken outthrough the insulating enclosure of the tube to serve as cathodeconnection.

The present invention relates to cathodes of this type, particularly tothose of which the radial and/or axial dimensions do not exceed theorder of magnitude of a few milimeters.

It is known that the skirt cools in a nonnegligible manner the emissivesurface, at the same time by radiation and by thermal conduction to thesolid or rigid support. It has already been proposed in the FrenchPatent No. 1,053,508, of Apr. 7, 1952, assigned to the assignee ofthepresent application, to remedy this inconvenience by providing withina portion of the skirt slots cut into a solid metallic wall. However,this solution, which is applicable when the dimensions of the skirt aresufficiently large, is totally unrealizable when these dimensions are ofthe order of a few millimeters, for obvious technological reasons.

The present invention has as aim the realization of a skirt for cathodesof millimetric dimensions which avoids the technological difficulties ofthe known system while preserving a rigidity suiiicient to maintainfirmly the emissive surface of the cathode.

Accordingly, it is an object of the present invention to provide acathode structure of the type described hereinabove involvingmillimetric dimensions which obviates the shortcomings and inadequaciesencountered with the prior art constructions when applied to tubes ofsuch dimensions.

It is another object of `the present invention to provide a cathodestructure, and more particularly a skirt for supporting the emissivestructure on a rigid support which may be readily used with cathodestructures of millimetric dimensions and which may be readilymanufactured without Igreat expenditures or dificulties.

A further object 4of the present invention resides in the provision of acathode structure involving millimetric dimensions which is simple,prevents excessive heat losses either by radiation or thermal conductionyet assures sufficient rigidity to maintain the cathode structure inplace.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, two embodiments in accordance with thepresent invention, and wherein FIGURE 1 is an axial cross sectional Viewthrough a cathode provided with a skirt in accordance with the presentinvention;

FIGURE 2 is a perspective view of one embodiment of a skirt inaccordance with the present invention, and

FIGURE 3 is a perspective view of another embodiment of the skirt inaccordance with the present invention.

Referring now to the drawing wherein like reference numerals are usedthroughout the various views to designate like parts, and moreparticularly to FIGURE l,

3,2l585 Patented Nov. 2, 1965 ICC reference numeral 1 designates thereinan emissive cathode which, in the illustrated embodiment, is in the formof a disk, heated by the intermediary of a heating cylinder 2, itselfheated by a ilament 3.

The assembly so far described is supported by the skirt 4, fixed on asolid support 5, in the form of a disk sealed between two cylinders 6and 7, for example, of ceramic material and forming part of the envelopeof the tube. A shield 8 is disposed about: the skirt 4 to limit therediation of the heating cylinder 2.

The skirt 4 has a diameter of the order of 2 to 4 millimeters and aheight also of the order 2 to 4 millimeters.

In the known prior art cathodes of such dimensions, the skirt wasconstituted by a solid metal cylinder with a thickness of the order of 5to l5 microns. Not only a heat loss by flow to the support resultedtherefrom, as the piercing of slots according to the aforementioned`French Patent 1,053,508 was impossible fby reason of the smallness ofthe dimensions, but also there resulted a difculty in proper assemblyand welding of the skirt to the emissive element and the support.

According to the present invention, the skirt 4 is realized as agrid-like structure ma-de of wires of which two embodiments areillustrated in perspective in FIGURES 2 and 3. In FIGURE 2, the skirt 4is formed by two layers of wires wound in opposite directionstangentially to a cylinder surface whereby the wires of each layer areparallel. The wires are brazed to each other at each point of contactsuch as 9.

In FIGURE 3, the skirt 4 is formed by a series of wires 10 disposedalong the generatrices of a cylinder on which is wound in helix formanother series of parallel wires 11. For example, the wires l0 may be oftungsten with a diameter of 25 microns spaced from one another by 0.4millimeter, and the Wires 1l may also be of tungsten of 64 microns indiameter.

Tests have shown that the skirts in accordance with the presentinvention which may be manufactured automatically with the aid ofmachines known under the name of winding machines, combined with abrazing furnace, diminish very considerably the losses by ow of heat andconsequently reduce the heating power necessary for proper operation ofthe tube while simultaneously preserving a mechanical resistance atleast equal to that of the skirts made of plain or solid metal ofcomparable dimensions, taking into consideration the inevitablecrumbling or wrinkling thereof during the operations of theiremplacement and being at the same time more easy to manufacture and tosecure without major damage.

While I have shown and described two embodiments in accordance with thepresent invention, it is understood that the same is not limitedthereto, but is susceptible of many changes and modifications Within thespirit and scope thereof as known by a person skilled in the art. Thus,the present invention is in particular applicable also to cathodes ofwhich the emissive element has the form of a cylinder of which theperiphery is supported by the skirt. Other configurations of woven gridstructures brazed at the cross-over points are comprised within thescope of the present invention to the extent that the configurationthereof has recourse only to currently known, conventional techniques.Additionally, the selection of materials and dimensions is also left tothe appreciation of a technician skilled in the art without the exerciseof invention.

Thus, while I have shown and described two embodiments in accordancewith the present invention, it is obvious that the same is not limitedthereto, but is susceptible of many changes and modifications within thespirit and scope thereof, and I therefore do not wish to a be limited tothe details shown and described herein, but intend to cover all suchchanges and modifications as are encompassed by the scope of theappended claims.

I claim: 1. An indirectly heated cathode assembly for electron dischargedevices, comprising:

first substantially cylindrical hollow support means having dimensionsin length and diameter thereof of the order of a few millimeters,heating means within said hollow support means, electron emissive meanssecured to said rst support means, and second substantially cylindricalsupport means secured to the periphery of said tirst support means andformed by a grid-like structure of line wires. 2. An indirectly heatedcathode assembly for electron discharge devices, comprising:

first substantially cylindrical hollow support means having dimensionsin length and diameter thereof of the order of a few millimeters,heating means within said hollow support means electron emissive meanssecured to said iirst support means, and second substantiallycylindrical support means secured to the periphery of said first supportmeans and formed by a grid-like structure of tine wires wound insubstantially opposite directions approximately tangentally to asubstantially cylindrical surface. 3. An indirectly heated cathodeassembly for electron discharge devices, comprising:

lirst substantially cylindrical hollow support means having dimensionsin length and diameter thereof of the order of a few millimeters,heating means within hollow support means electron emissive meanssecured to said rst support means, and second cylindrical support meanssecured to the periphery of said first support means and formed by agrid-like structure of line wires, one series of said wires beingdisposed substantially along the generatrices of a cylinder, and anotherseries of wires wound over the wires of said series. 4. An indirectlyheated cathode assembly for electron discharge devices, comprising:

rst substantially cylindrical hollow support means having dimensions inlength and diameter thereof of the order of a 'few millimeters, heatingmeans within said hollow support means, electron emissive means securedto said lirst support means, and second substantially cylindricalsupport means secured to the periphery of said first support means andformed by a grid-like structure of line tungsten wires of the order l to95 microns in diameter wound in substanially opposite directionsapproximately tangentially to a substantially cylindrical surface.

5. An indirectly heated cathode assembly for electron discharge devices,comprising:

first substantially cylindrical hollow support means having dimensionsin length and diameter thereof of the order of a few millimeters,heating means within said hollow support means, electron emissive meanssecured to said first support means,

and second cylindrical support means secured to the periphery of saidfirst support means and formed by a grid-like structure of line tungstenwires, one series of said wires of about 25 microns in diameter beingdisposed substantially along the generatrices of a cylinder, and anotherseries of wires of about 64 microns in diameter wound over the wires ofsaid first series.

6. In an indirectly heated cathode structure having a cathode emissiveportion adapted to emit electrons upon application of heat, a relativelylixed hollow support for said portion, heating means within said supportand a supporting structure supporting the electron emissive portion onthe support,

the improvement essentially consisting of said supporting structurehaving dimensions of the order of a few millimeters and constituted by agrid-like network of line wires securely fixed t0 each other at crossover points.

7. An indirectly heated cathode assembly for electron discharge devices,comprising:

first substantially cylindrical hollow support means having dimensionsin length and diameter thereof of the order `of a few millimeters,heating means within said hollow support means, electron emissive meanssecured to said first support means,

and second cylindrical support means secured to the periphery of saidrst support means and formed by a grid-like structure of line tungstenwires, one series of said wires of about 25 microns in diameter beingdisposed substantially along the generatrices of a cylinder, and anotherseries of wires of about 64 microns in diameter wound substantiallyhelically over the wires of said rst series, the wires of said anotherseries being spaced from each other by a few tenths of a millimeter.

References Cited by the Examiner UNITED STATES PATENTS 2,516,841 8/50Arditi et al. 313--348 2,882,436 4/59 Dorgelos 313-346 FOREIGN PATENTS653,707 5/51 Great Britain.

DAVID J. GALVIN, Primary Examiner.

1. AN INDIRECTLY HEATED CATHODE ASSEMBLY FOR ELECTRON DISCHARGE DEVICES,COMPRISING: FIRST SUBSTANTIALLY CYLINDRICAL HOLLOW SUPPORT MEANS HAVINGDIMENSIONS IN LENGTH AND DIAMETER THEREOF OF THE ORDER OF A FEWMILLIMETERS, HEATING MEANS WITHIN SAID HOLLOW SUPPORT MEANS, ELECTRONEMISSIVE MEANS SECURED TO SAID FIRST SUPPORT MEANS, AND SECONDSUBSTANTIALLY CYLINDRICAL SUPPORT MEANS SECURED TO THE PERIPHERY OF SAIDFIRST SUPPORT MEANS AND FORMED BY A GRID-LIKE STRUCTURE OF FINE WIRES.